Frost control



A. BLOOM FROST CONTROL Jan. 4, 1938.

Filed Sept. 26, 1935 FIG.

INVENTOR ?,77,JZM, ATTORNEY Patented Jan. 4, 1933 NiTE Newark Refrigeration d Applies 6a.,

Placid, hi. .i., a corporation oil New fierce? Application September 26, 1935, genial No. 42,1i9li The invention relates to improvements in mechanical refrigerators and particularly to an autotically operating defrosting mechanism adapted for use as an adjunct to, or an integral part of, refrigerating systems in common use at the present time.

A primary object of the invention is to promote and increase the efliciency of a mechanical refrigerator by preventing the formation of an excess coating of frost or ice on the evaporator. Heretofore, it has been customary for a user to throw out a switch or other master control element whenever he believed too much ice had collected upon the evaporator unit.

That mode of frost control left the matter entirely to the discretion of the user with the resuit that the compressor unit or its equivalent, operated, in the meantime, more frequently and through periods of greater duration thanneces sary, for the reason that the relatively thick layer of ice that had accumulated on the evaporator acted as a blanket and effectively prevented the unit from efficiently performing its intended functions.

Another disadvantage found with refrigerators requiring the attention of the user to defrost the evaporator was that the user had no sure way of knowing just when the unit should be stopped and defrosted. Frequently, the only indication to the user that the coil needed defrosting came afterthe freezer coil had become excessively coated with ice and unpleasant odors emitted from the food compartment or contamination notice in other foods.

When that occurred the box was turned off to allow the evaporator to defrost. That act introduced another hazard in the proper refrigeration of foodstuffs. The user would forget to turn the box on again until sometime after the temperature inside had risen to the point conducive to the growth of harmful bacteria.

By the old method the ice cubes within the freezing compartment also liquefied and the water absorbed the odors of the box. In consequence, the user was without ice until some time after the box was again turned on; and unless the trays were emptied and refilled with fresh water, the ice the user did eventually obtain was unsavory and ill flavored.

The present invention aims to overcome the disadvantages and inconveniences experienced with the defrosting arrangements in common use by relieving the user of the necessity of periodically turning off of the'box and remembering to turn it on again.

(Cl. 6H)

Another object of the invention is to render available a thermo responsive element that is sensitive and quickly responsive to changes in temperature, and a device that may be inexpensively constructed, simple in its operation, and extremely reliable and dependable in the performance of its complicated functions. And by way of additional refinement to render available a frost control instrumentality that may be quickly adapted andinstalled in cooperative relation with the evaporator and temperature controlling mechanism of a conventional refrigerator.

In accomplishing the objects of this invention it is proposed to arrange an auxiliary thermo responsive control device in series relation with the customary temperature control mechanism. The auxiliary control means being so adjusted that when the temperature adjacent the evaporator reaches a given degree the usual temperature control mechanism of the refrigerating system is rendered ineffective and ceases to control the periodic starting and stopping of the refrigerating apparatus.

Ordinarily, the usual temperature controlling mechanism of the system is set so that when the temperature at the evaporator is 12 or colder, the refrigerating apparatus is not running, and when the temperature at the evaporator is at or about 28 the mechanism starts to function and reduces that temperature to about 12.

The temperature of the evaporator, however, does not indicate the temperature of the air surrounding it, otherwise the foodstuffs kept in the refrigerator would be frozen. Since air is a very poor conductor of heat, the temperature control is set to produce a low temperature at the evaporator to keep the temperature of the box proper below 50.

In the process of cooling, water is given off and it is the water content of the air adjacent the evaporator that condenses and freezes upon the colder surface thereof. This condensation and freezing continues until a layer of surface ice builds up to a. point that effectively interferes with the efiiciency of the evaporator. That is to say, the evaporator itself may have one temperature but the temperature 'at the surface of the surrounding blanket of ice is substantially higher. Thus, poor circulation of the air within the box is induced which results in the box having a bad odor.

The present invention proposes an automatically operating frost control incorporating an auxiliary thermo responsive control mechanism arranged in series relation with the usual temperature control. The auxiliary control is so designed and positioned relative to the elements of the refrigerating system, that the thickness of the frost blanket on the evaporator is the primaryfactor in determining the proper time to defrost. The time period elapsing between defrosting cycles varies with each installation and with the character of foodstuffs being preserved. However, by arranging the auxiliary control in a manner that it is responsive to a distance and temperature factors, a frost control is provided that automatically defrosts the evaporator whenever the accumulation of frost tends to exceed a given amount.

In this way there is provided a frost control that operates entirely automatically and keeps the evaporator substantially free of frost with consequent savings in operating power as the refrigerating apparatus may operate more efficiently at all times. Likewise, with a substantially clean evaporator odors are noticeably absent and better and faster circulation of air within the refrigerator results.

Other objects and advantages will be in part indicated in the following description and in part rendered apparent therefrom in connection with the annexed drawing.

To enable others skilled in the art so fully to apprehend the underlying features hereof that they may embody the same in the various ways contemplated by this invention, a drawing depicting a preferred typical construction has been annexed as a part of this disclosure and, in such drawing, like characters of reference denote corresponding parts throughout all the views, of which:-

Figure 1 represents a conventional refrigerator embodying this invention.

Figure 2 is an enlarged view of the evaporator unit of the refrigerator illustrated in Fig. 1, and showing more clearly the location and a method of attachment of the frost control device.

Figure 3 is an enlarged detail of the thermo responsive element of the frost control mechamsm.

Figure 4 is a modified form of thermo responsive element. Q

Figure 5 is a schematic diagram of a representative refrigerating system embodying principles of this invention.

Referring more particularly to the drawing,

Fig. 1 thereof represents a conventional refrigerator embodying this invention. The evaporator ID or freezing coil, as it is sometimes called, is located in the upper portion of the box II, and is supplied periodically with a refrigerant in any well known manner. In this particular disclosure, an electrically driven compressor [2 is illustrated as one means for supplying the evaporator with a liquefied refrigerant. Other types of refrigerating apparatus may be employed, however,

without departing from the principles underlying this invention.

Associated with the'evaporator I is the conventional temperature control mechanism I! which controls the cycle of operation of the compressor. The usual temperature control mechanism comprises essentially a thermometer bulb l4 strapped or otherwise secured to the upper portion of the evaporator ID, a bellows or power element I operated thereby, a spring operated switch lever 16 which is actuated in one direction by the bellows and in the opposite direction by a loading spring H. The switch lever IS, in

turn, makes or breaks the circuit to a motor l8 that propels the compressor device l2. A manually operated dial is is provided for adjusting the tension of the loading spring i1 thereby to control the point whereat the compressor starts functioning to withdraw and compress the gas in the evaporator. Usually, the device is set so that when the temperature of the evaporator is in the neighborhood of 28 the thermostat clicks on and starts the compressor. When the compressor has operated a length of time sufficient to reduce the temperature of the evaporator to about 12 the thermostat clicks off and stops the compressor. A differential adjusting screw means 20 is usually provided for initially setting the off position of the apparatus.

A master switch l3a built into the temperature control- I3 is also customarily provided for permanently cutting ofi the power or whenever it is desired to stop the apparatus as for purposes of defrosting the evaporator.

The foregoing briefly describes the temperature control mechanism of a mechanical electrical refrigerator, elements equivalent in function and purpose also being incorporated in other mechanical refrigerating systems such as those powered by gas, and will suflice to illustrate the principles and adaptation of the present invention.

The customary control of the common refrigerator, does not, it will be seen, provide for any means for defrosting the evaporator, save by the master control switch l3a. In consequence, a user does not know when to defrost the coil, or how long it takes to defrost, or when to turn the refrigerator on again. With such devices ineflicient operation and unsatisfactory results follow, a few of which have been set forth above.

The aim of the present invention is to supply, a deficiency long needed in the common refrigerator, namely that of providing for an eflicient, automatically operating, frost control, and a control which when once installed and set in operation does not interfere with or hamper the users control over the-temperature range within the food compartment of the refrigerator. A preferred form of a device for accomplishing that end consists. of a controller 26 which comprises a thermo responsive element 2| arranged to operate a bellows or power element 22, which in turn actuates a control lever 23. In the embodiment disclosed the control lever 23 carries electrical switch contacts 24 arranged to open or close the circuit in the power line 25 to the mo tor I8. Thecontroller 26, it will be 'noted, is

placed in serie's relation 'with the controller l3, and accordingly the frost control 26 dominates and controls the effective action of the temperature control II.

The thermo responsive element 2| preferably comprises a bulb 21 and a plate member 28 secured thereto for the purpose of increasing the heat inductance capacity of the bulb.

Thebulb 21 and its plate 28 is placed in spaced relation with the lower portion of the evaporator Ill, and heat insulated therefrom. Fig. 2 of the drawing illustrates a preferred method of mounting the bulb to the evaporator which. comprises a bracket member 29, provided with one or more studs 30. The thermal element 2| is mounted upon the studs 30 and maintained in spaced relation therefrom and also from the bracket 25 and sidewall Illa of the evaporator by meanscit fibrous washers and spacers 3|. In, the present disclosure the bracket 29 extends forward and around the front of the evaporator and is secured til aroaaro to the door frame lllb as by means of screws the. Fig. 3 illustrates another method of attachment in which the plate it is secured to studs directly to the side ltd of the evaporator.

Thespacing between the plate it and the side wall We of the evaporator, is an important factor in the operation of the frost controlling mechanism, for it is this distance which determines the thickness that the frost blanket is permitted to reach before the defrosting cycle begins.

I have found that by placing the plate Elli approximately an eighth of an inch away from the side of the evaporator, very satisfactory results are obtained. That distance, however, is subject to variation depending upon the style of refrigerating system and/or the thickness of the ice blanket desired.

The controller it, above referred to, is provided with an adjustable loading spring 332 which may be set by the handle 33 to the desired on position, and also a differential adjusting screw 35% which may be set to the desired d position.

Normally the frost control 265 is adjusted so that the circuit to the motor to is open when the temperature at the element ill falls to approximately 22-25 degrees and is closed when the temperature at the element 28 is approximately 38-40 degrees. These temperature values may be altered by the adjusting means or and 36 to suit the particular conditions of the installation.

When the proper setting has been obtained, however, the device operates as follows:

Starting with a hot bolt, the control arm 23 of the frost control it} is in its effective position. in the present illustration the effective position is. the position wherein. the contacts 2d are closed thus completing a portion of the circuit to the motor Elli. With a hot box the control element iii of the usual temperature control device it will likewise be in its effective position and by closing the master switch film, the circuit to the motor is completed and the refrigerating de-- vice starts operating. The refrigeration process continues until the temperature of the evaporator reaches approximately 12 degrees. At that point the usual temperature control device it cuts out the motor and the refrigerating mechanism stops. The temperature at the evaporator then proceeds to rise due to the absorption of heat from the rest of the box, until it reaches approximately 28 degrees and the refrigerating device is again rendered efiective and lowers the temperature.

This cycle repeats itself continuously whereby there is maintained a temperature of something under 50 in the food storage compartment of the refrigerator. the evaporator it gradually collects a layer of frost which ordinarily increases in thickness to the point of edectively interfering with proper refrigeration. That is prevented. however, with the incorporation of the frost troll device fL-fii. as before mentioned the plate 2d of the thermal element is spaced approximately to of an inch from the surface of the evaporator, and

preferably at the lower portion thereof, and being heat insulated therefrom, does not take the temperature of the evaporator but assumes more. or less the temperature of the box. The frost layer on the evaporator builds up until its proximity with the plate reduces the temperature of the bulb carried thereby to approximately22-25 degrees. When that occurs the secondary controller z fi-operates automatically end renders the During the process, however,

refrigerating apparatus l2 ineffective, i. e. by opening the circuit to the motor it.

The refrigerating apparatus, therefore, cannot operate as long as the secondary control is in its open or ineffective position and accordingly the evaporator starts to defrost. Defrosting begins at the top or warmest portions of the evaporator and the ice water produced during the process runs down the side of the evaporator. The running ice water floods the plate 2d and maintains the pate at or about freezing temperature until substantially all of the frost blanket has melted and run ofi.

By placing the plate 2d at a low point on the evaporator one is assured that the frost will be entirely melted before the controller it operates to cut in the refrigerating apparatus. As the defrosting process nears its end a few drops of water are found bridging the gap between the plate 25.8 and the wall too of the evaporator. These ice water bridges serve also to keep the plate 2d at a low temperature which insures substantially complete defrosting.

Perpendicular to the plate 2t, and extending in a direction away from the evaporator, a plurality of fins 28a are provided. The fins the project into the atmosphere of thebox proper and serve as heat collectors. That is, the temperature of the fins more nearly approaches the temperature of the air of the box proper and as soon as the ice water stops running against the plate til, the plate 2t quickly takes the temperature of the fins and transmits the heat to the bulb ill. The bulb, in turn, responds and causes the controller 233 to be actuated to its effective position, thus completing the circuit to the refrigerating apparatus 02. It will be understood that during the defrosting process, the temperature of the evaporator ill rises and the temperature control it moves to its normal effective position. With the secondary control in series therewith, the movement of the first control to its efiective position has no efiect upon the starting of the refrigerating apparatus because of the domination exercised by the frost control iii over the temperature control iii.

After the evaporator has become defrosted the refrigerating apparatus automatically operates to repeat its normal refrigerating cycle which continues until another frost blanket is formed. As each subsequent frost blanket reaches the thickness required to lower the temperature of the thermal element if the required amount, the defrosting cycle again automatically starts functioning.

By this fully automatic control, the box defrosts itself periodically without any attention whatever from the user. rator retain their solid state throughout the 1 process, for the reason that the box is off only the actual time necessary to defrost the evaporator and the temperature within the evaporator never rises above the freezing point.

Likewise the temperature within the food compartment is continually maintained below the 50 line because of the 38-40 degree setting given to the secondary controller 26.

The ice cubes within the evapo- In this way there is provideda fully automatic compartment, and promoting safe and efficient food preservation.

Without further analysis, the foregoing will so fully reveal the gist of this invention that others can, by applying current knowledge, readily adapt it for various utilizations by retaining one or more of the features that. from the standpoint of the prior art, fairly constitute essential characteristics of either the generic or specific aspects of this invention and, therefore, such adaptations should be, and are intended to be, comprehended within the meaning and range of equivalency of the following claims.

Having thus revealed this invention, I claim as new and desire to secure the following combinations and elements, or equivalents thereof, by Letters Patent of the United States:

1. In an electrical refrigerator, an evaporator, motor operated means for circulating a refrigerant in the evaporator, a motor circuit, control means for said motor means including a switch in said circuit, temperature responsive means normally operative to actuate said switch including a temperature responsive element strapped to the side of said evaporator, said temperature control means normally operating between predeter mined upper and lower limits thereby to maintain the temperature of said evaporator between said limits, and defrosting means for said evaporator comprising a normally closed second switch means in series with said first mentioned switch, a second temperature responsive means for actuating said second switch, including an ele- 'ment secured in fixed spaced relation with the side of said evaporator and at the lower edge thereof and in the path of the down flow of ice water, said last mentioned element being spaced from the side of the evaporator to provide an air space therebetween substantially equal to a layer of frost of a predetermined thickness and said second temperature responsive means being operative to actuate said second switch to an open position, thereby to render said circulating means inoperative, when the layer of frost exceeds said thickness, said element further operating to maintain, said second switch open until the ice Water incident tothe defrosting operation ceases to flow over the said element.

2. A temperature responsive element for controlling a defrosting cycle of a refrigerator having an evaporator and means for circulating a refrigerant therein, and temperature responsive means normally operative between upper and lower temperature limits to maintain the temperature of said evaporator between said limits, comprising a second thermo-responsive switch mechanism for controlling said circulating means including a thermostat bulb connected with said switch operative selectively to open and close said switch, said bulb being immovably positioned in spaced relation close to the lower portion of a surface of the evaporator so as to be flooded with ice water during a defrosting cycle, said second thermo-responsive means operating to render said 1 refrigerant circulating means, ineffective when the layer of frost on the evaporator approaches and reduces the temperature of said thermostat bulb to a predetermined value, a metal plate member integral with said bulb, said plate member extending parallel to the plane of the surface of the evaporator, and a series of metal fin members projecting laterally from said plate into the surrounding air for collecting and transmitting tosaid plate and bulb the tempera.-

ture of said air upon the cessation of flow of ice water over said plate.

3. A refrigerator combining a corrugated evaporator; means for circulating a refrigerant therein; a temperature controlling mechanism for said means normally operative between predetermined upper and lower limits to maintain the temperature of said evaporator between said. limits; 9. frost controlling mechanism for said evaporator comprising an elongated second temperature responsive element rigidly mounted in spaced relation to the side wall of said evaporator near the lower marginal edge and transversely to the corrugations thereof, the spacing of said element from the side wall of the evaporatorbeing such as to permit the flow of ice water incident to a defrosting operation to flow thereover; means for insulating said element from said evaporator; and means actuated by said second temperature responsive element when the layer of frost ac-' cumulating on the evaporator approaches said element and reduces the temperature thereof to a predetermined minimum for rendering said circulating means ineffective and to maintain the said means ineffective until the ice water incident to defrosting ceases to flow over the said element, and thereafter to render said circulating means effective to reduce the temperature of said evaporator to its said lower limit.

4. A refrigerator combining an evaporator, means for circulating a. refrigerant therein, a temperature controlling mechanism for said means normally operative between predetermined upper and lower limits to maintain the temperature of said evaporator between said limits, a frost controlling mechanism for said evaporator comprising a second temperature responsive element rigidly mounted in spaced relation to the extreme lower side wall of said evaporator and insulated therefrom, the spacing of said element iromthe wall of the evaporator being such as to permit the flow of ice water incident to a defrosting operation to flow over said element; and means actuated by said second temperature responsive element when the layerof frost accumulating on the evaporator approaches said element and reduces the temperature thereof to a. predetermined minimum to render said refrigerant circulating means ineffective and to maintain the said means ineffective until the ice water incident to defrosting ceases to flow over the said element.

5. A refrigerator combining a corrugated evaporator; means for circulating a refrigerant therein; a temperature controlling mechanism for said means normally operative between predetermined upper and lower limits to maintain the temperature of said evaporator between said limits: 9. frost controlling mechanism for said evaporator comprising an elongated second temperature responsive element rigidly mounted in spaced relation to the side wall of said evaporator near the lower marginal edge and transversely to the corrugations thereof, the spacing of said element from the side wall of the evaporator being such as to permit the flow of ice water incident to a defrostingoperation to flow thereover; means for insulating said element from said evaporator;

and means actuated by said second temperature responsive element when the layer of frost accumulating on the evaporator approaches said element and reduces the temperature thereof to a predetermined minimum for rendering 'said circulating means ineffective and to maintain the said means ineffective until the ice water incident to defrosting ceases to flow over the said element.

aioaaie and thereafter to render said circulating means effective to reduce the temperature of said evaporator to its said lower limit; said second temperature responsive element including a thermostat bulb and a corrugated metal plate member integral therewith disposed parallel to the wall of the evaporator and interpenetrating but not contacting the corrugations of the surface thereof, said corrugated plate member serving as a conductor for uniformly transmitting to said thermostat bulb the surface temperature of a substtial area of the corrugated evaporator.

8. A refrigerator combining an evaporator, means for circulating a refrigerant therein, a temperature controlling mechanism for said ans normally operative between predetermined upper and lower limits to maintain the temperature of said evaporator between said limits, a iirost controlling mechanism for said evaporator comprising a second temperature responsive element tilt mounted in spaced relation to the reme lower side wall of said evaporator and insulated therefrom, the spacing of said element from the wall of the evaporator being such as to permit the flow of ice water incident to a defrosting operation to flow over said element; and meansactuated by said second temperature responsive element when the layer of frost accumulating on the evaporator approaches said element and reduces the temperature thereof to a predetermined minimum to render said refrigerant circulating means inefl'ective and to maintain the said means ineffective until the ice water incident to defrosting ceases to flow over the said element, said second temperature responsive element including a thermostat bulb and a metal plate member integral therewith and a series of metal fins projecting laterally from said plate member, said fins serving as heat collectors for quickly transmitting to said plate and thence to the said thermostat bulb the temperature of the air surrounding the evaporator upon cessation of the flow of ABBA 1 BLOOM. 

